<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            width: 400px;
            height: 400px;
            margin: 0 auto;
            border: 10px solid green;
            /* 设置渐变 */
            background-image: -webkit-radial-gradient(green,yellow,red);
            /* 圆形 */
            /* background-image: -webkit-radial-gradient(circle,red,yellow,blue); */
            /* 椭圆形,不支持 */
            /* background-image: -webkit-radial-gradient(ellipse,red,yellow,blue); */
            /* 设置渐变位置 */
            /* background-image: -webkit-radial-gradient(200px circle, red,yellow,blue); */
        }
    </style>
</head>
<body>
    <div class="box">
    </div>
</body>
</html>